Reinforced flexible tubing is used in a variety of important commercial applications. One of the more important applications for such reinforced tubing is in tubular medical devices, for example, catheters. Catheters are generally designed for insertion into canals, vessels, passageways or body cavities so as to permit injection or withdrawal of fluids or other materials. For example, such catheters may be used to introduce medicinal compositions into a patient's bloodstream. In other cases, the catheters may provide a stable, secure passageway for passing solid materials, such as guide wires, angioplasty balloons and stents into a patient's body. In such cases the catheters, which are sometimes referred to as "introducer sheaths," desirably possess a relatively low friction inner surface which facilitates movement of the solid materials through the introducer sheath. In many applications, this low friction inner surface is provided by a relatively thin-walled tubular liner comprised of low friction material.
Catheters are generally engineered to accommodate various, often countervailing, requirements. For example, it is generally required that catheters are flexible and possess good mechanical integrity, including burst-strength. In addition, it is generally required that catheters possess substantially small diameters so that they may be inserted into restricted body passageways, for example, blood vessels. Such small diameter catheters generally comprise an inner surface of substantially thin walled tubing to provide an opening through which fluids or solids are injected or withdrawn. However, such thin-walled tubing is generally prone to bursting and/or mechanical deformation, for example, wall collapse or kinking, resulting in flow reduction or stoppage.
To overcome the tendency of thin-walled catheter tubing to deform mechanically, the tubing is generally reinforced. The reinforcing of such tubing typically comprises covering the tubing with braided coverings which include a plurality of interwoven strands of wires. Such reinforced tubing is disclosed, for example, in U.S. Pat. Nos. 3,485,234; 4,567,917; and 5,002,559, each of which is incorporated herein by reference.
However, reinforcing thin-walled tubing with a covering of woven or braided wires is problematic. For example, the ready deformation of the thin-walled tubing is such that it is generally difficult to maintain the mechanical integrity of the thin-walled tubing while the braided covering is being wound onto or applied to the tubing. Thus, the tubing is subject to deformation during the reinforcement process.
To overcome the problems associated with methods for reinforcing thin-walled tubings, prior art techniques utilize a substantially rigid mandrel which is typically inserted into the tubing prior to the reinforcing process. The mandrel prevents the deformation of the tubing which would otherwise result from the mechanical stresses that occur during the reinforcement process.
However, the technique of inserting a mandrel into the tubing during reinforcing procedures suffers from serious drawbacks. For example, the length of tubing which may be reinforced during any given reinforcing procedure is generally dictated by the length of the mandrel. Thus, reinforcing a substantially long distance of tubing requires a correspondingly long mandrel. The requirement of such long mandrels imposes process limitations and results in increased manufacturing costs. Furthermore, the use of such a solid mandrel is generally very expensive as a result of the stringent tolerance requirements which must be met in order for such a mandrel to effectively reinforce the thin-walled tubing without itself causing destructive deformation of the thin-walled tube.
Accordingly, it is an object of the present invention to provide improved methods for reinforcing thin-walled tubing.
It is a further object of the present invention to provide cost-effective reinforced thin-walled tubing.
It is yet a further object of the present invention to provide methods for reinforcing thin-walled tubing which involve simple processing techniques.
These and other objects of the present invention will become apparent from the detailed description of preferred embodiments which follows.